This proposal is a broad based investigation of the physiology of placental lactogen. In previous studies from this laboratory, ovine placental lactogen (oPL) has been demonstrated to have potent growth promoting activities in vivo and in vitro which are comparable to those of growth hormone. Over the next year, studies will be performed to investigate the effects of oPL administered directly to the fetus on plasma somatomedin concentrations and liver ornithine decarboxylase activity as well as on the concentrations of various hormones and substrates involved in carbohydrate, lipid, and protein metabolism. Additional studies will focus on the mechanisms controlling the synthesis and secretion of human placental lactogen by placental explants. To date, the factors regulating the synthesis and secretion of placental lactogen are unclear. Initial studies will focus on the role of prostoglandins and alpha and beta adrenergic agents. These studies are of importance since numerous investigations indicate aberrations of placental lactogen secretion in pathologic pregnancies associated with diabetes mellitus, pre-eclampsia, and intra-uterine growth retardation.